The present disclosure relates to centrifugal compressors, such as used in turbochargers, and more particularly relates to centrifugal compressors that include a compressor recirculation system employing a recirculation valve for regulating the recirculation of air from the compressor discharge to the compressor inlet.
Compressors in vehicle turbochargers are prone to surge during certain operating conditions such as low-flow rate, high rotational speed conditions (e.g., when the engine and turbocharger are operating at high speed and relatively open throttle and the driver takes his foot off the accelerator pedal so as to suddenly reduce the air flow demanded by the engine).
To reduce the likelihood of surge, it is known to employ a compressor recirculation system, which bleeds off a portion of the pressurized air from the compressor discharge volute and recirculates it back into the compressor inlet. The recirculation system employs a recirculation valve disposed between the compressor discharge volute and the compressor inlet, and a recirculation duct leading from the recirculation valve into the compressor inlet. In a typical prior-art type of recirculation system, the compressor inlet recirculation duct is a round or nearly round cylindrical volume.